Available light. Strictly speaking, existing light covers all natural lighting from moonlight to sunshine. For photographic purposes, existing light is the light that is already on the scene or project and includes room lamps, fluorescent lamps, spotlights, neon signs, candles, daylight through windows, outdoor scenes at twilight or in moonlight, and scenes artificially illuminated after dark.

The light that is naturally illuminating a scene without any additional light that has been added by the photographer. Ambient light and available light are two other terms that mean the same thing. A tricky play of light and shadow presents a challenge to obtaining proper EXPOSURE.